The overall goal of this project is to characterize and stimulate the control of phonation in vocal tremor. The working hypothesis around which the project is organized proposes the vocal tremor results from modulation of vocal fold vibration due to an interaction between central and peripheral oscillators that control (or undermine control of) the voice and speech mechanism. This project focuses on one aspect of the system, vocal fold vibration and the control of voice production at a peripheral (laryngeal) level. The specific aims to be accomplished during this period are as follows: 1) Determine the physiological basis for laryngeal biomechanics in production of vocal tremor through measurement of laryngeal muscle activity, subglottal pressure, and respiratory movement patterns. 2) Investigate the role of peripheral reflex feedback loops in vocal tremor modulation through system perturbation via electrical stimulation of laryngeal muscles. 3) Simulate vocal tremor with computer models of phonation, using a) hypothetical input parameters for laryngeal stiffness and subglottal pressure, and b) the same physiological input parameters from patient recordings incorporated into the models, and comparison of simulations with patient data. This training grant focuses on acquisition of skills and experience in laryngeal modeling and phonation simulation. Training will be gained in electromyographic signal analysis, multi-channel recording and instrumentation for speech research, and statistics and research design. The project will also be heavily computer-oriented and investigate an area of laryngeal modeling that is relatively unexplored, phonatory control under pathological conditions. Theoretical studies will examine modulations in laryngeal stiffness, subglottal pressure, phase, and muscle activation, their effects on modulation (amplitude and frequency) of vocal fold oscillation, and develop feedback loops to simulate hypothesized peripheral oscillators. The experimental phase consists of studies of neuromuscular and respiratory input to the larynx. This information about vocal tremor will be applied to model simulations with the use of physiological signals as input model parameters.